1. Field of the Invention
The present invention relates generally to antenna alignment and monitoring, and in particular to a system and method for antenna alignment and monitoring using global navigation satellite system (GNSS) signals.
2. Description of the Related Art
Wireless telecommunications, such as cellular, DCS, GSM, TDMA, CDMA, etc., use line-of-site antennas, which are commonly elevated on towers and mounted on tall buildings for maximizing coverage and range. Telecommunications antennas are typically directional, and require relatively precise directional alignment for optimal performance. For example, cellular telecommunications antenna systems typically include multiple, individual telecommunications antennas for transmitting and receiving. The antennas are commonly grouped in arrays or patterns configured for optimizing performance. Telecommunications antennas are commonly adjustable for both altitude (i.e., tilt in a vertical plane) and azimuth (i.e., alignment or “heading” in a horizontal plane).
Previously, cell tower antenna alignment was accomplished by rough approximation from ground level, e.g., by surveyors, followed by antenna-level fine alignment by skilled technicians using special equipment and techniques. Such previous antenna alignment procedures had a number of disadvantages. For example, they tended to be relatively expensive because the technicians were relatively highly-trained and the equipment was relatively sophisticated. Moreover, alignment technicians were required to ascend the towers and individually align the antennas one-by-one using iterative alignment-adjusting procedures, which tended to be time-consuming, particularly for installations with a number of antennas.
The Boucher U.S. Pat. No. 6,897,828 and U.S. Pat. No. 7,180,471 disclose another type of antenna alignment system and method using GNSS (GPS) receiver dishes mounted on frames, which in turn are temporarily mounted on the antennas for azimuth alignment. Multiple antennas in predetermined spaced relation can be used for computing azimuth by triangulating the GPS signals, or a single antenna can be moved from one location to another. However, the GPS receiver dishes and the aligning frames on which they are mounted must be relocated for aligning each separate antenna. Subsequent adjustments and realignments would require technicians to ascend the transmission towers for reattaching the alignment equipment to the individual antenna enclosures in order to obtain azimuth readings in real-time and adjust the antenna mountings accordingly.
A significant disadvantage associated with the aforementioned and other previous antenna alignment methods involved their inability to continuously monitor alignment and detect conditions of misalignment. Cell towers and other structures are susceptible to distortion and antenna deflection from various causes, such as weather, geological and impact forces, all of which can cause antenna misalignment. For example, after a major storm, cell towers and other antenna installations in an entire region may be affected and may be susceptible to performance degradation. Accordingly, an antenna alignment system should not only facilitate initial azimuth alignment, but also facilitate ongoing alignment monitoring and detecting conditions of misalignment, which can significantly deteriorate signal quality. Moreover, a permanent antenna alignment system should be contained primarily within existing equipment enclosures, such as the telecommunications antenna enclosures, because stringent regulatory requirements and approval procedures apply to equipment and components mounted exteriorly on transmission towers.
Heretofore there has not been available an antenna alignment system and method with the advantages and features of the present invention.